FIG. 2 shows one example of a power conversion system in which alternating current-and-direct current conversion device having the instantaneous voltage drop and service interruption counter-measure functions is equipped. In FIG. 2, 1 denotes the alternating current-and-direct current conversion device constituted by a DC/AC converter. A direct-current side of alternating current-and-direct current conversion device 1 is connected to a power storage section 2 such as a battery cell of a NaS (Natrium Sulfide) cell, a lead storage battery, lithium ion battery, and so forth and such as a capacitor of an electrolyte capacitor, an electric double layer capacitor, and so forth. 3 denotes an interconnection transformer. Alternating current-and-direct current conversion device 1 is connected to a power system 4 and an important load 5 via this interconnection transformer 3. 6 denotes a high-speed switch interposed in an electric passage connected to an electric power system 4, interconnection transformer 3, and important load 5. It should be noted that a power conversion system, hereinafter, called PCS) 10 is constituted by alternating current-and-direct current conversion device 1, power storage section 2, interconnection transformer 3, and a high-speed switch 6.
Ordinarily, an electric power is supplied from electric power system 4 to important load 5. However, if the instantaneous voltage drop or the service interruption is developed, a control device of PCS not shown in FIG. 2 opens high-speed switch 6 so that the electric power stored in power storage section 2 is supplied to important load 5 via alternating current-and-direct current conversion device 1 and interconnection transformer 3. In the way described above, a switch control permits a maintenance of the supply of electric power to important load 5 even if the instantaneous voltage drop or the service interruption is developed. Hereinafter, such a device as described above is called “instantaneous voltage drop and service interruption compensation device”. This device is commonly known as an uninterruptible power supply (“UPS”).
FIG. 3 shows a switch control block diagram during the instantaneous voltage drop and service interruption of the above-described “instantaneous voltage drop and power interruption compensation device”.
In FIG. 3, 21 denotes a deviation circuit which takes a deviation between a charge/discharge (electric) power command value and a charge/discharge (electric) power measured value, namely, a power detection value at a primary (winding) side (system side) of interconnection transformer 3 in FIG. 2. 22 denotes an APR control circuit which performs a control, with an output of deviation circuit 21 as input, to make it coincide with the charge/discharge power command value. 23 denotes another deviation circuit which takes the deviation between an alternating current detection value which inputs into and outputs from alternating current-and-direct current conversion device 1 in FIG. 2. 24 denotes an ACR control circuit which prepares a PWM command value of a current control, with an output of deviation circuit 23 as the input thereof.
These deviation circuits 21 and 23, APR control circuit 22, and ACR control circuit 24 constitute charge/discharge run PWM command value preparing section 20.
31 denotes still another deviation circuit which takes the deviation between PCS alternating current voltage effective value command value and PCS alternating current voltage effective value measured value, namely, a voltage detection value (an system interconnection voltage which is the same as important load 5) at the primary (winding) side (a system side) of interconnection transformer 3 in FIG. 2. 32 denotes an AVR control circuit which prepares an PWM command value to perform a coincidence control to make PCS alternating current voltage effective value coincident with its command value.
These deviation circuit 31 and AVR control circuit 32 constitute a self-contained run PWM command value preparing section 30 and AVR control circuit 32.
40 denotes a change switch which changes between charge/discharge run PWM command value preparing section 20 and self-contained run PWM command value preparing section 30 according to the charge-discharge run/self-contained run.
50 denotes a PWM control section which is prepared for a PWM control signal, namely, a gate signal of alternating current-and-direct current conversion device 1 shown in FIG. 2 on a basis of a command value changed according to change switch 40.
In FIGS. 2 and 3, any one of three run modes of “charge run” during which an electric power of a power system is charged into power storage section 2, “discharge run” during which the electric power of the power storage section is discharged from power storage section 2, and “stand-by run” during which neither charge nor discharge is performed is carried out.
It should, herein, be noted that these charge run, discharge run, and stand-by run are totally called “charge/discharge run mode”. During the charge run mode, change switch 40 in FIG. 3 is switched to charge/discharge run PWM command value preparing section 20. A controller, upon receipt of the charge/discharge electric power command value externally provided, performs a control (APR control) which makes the charge/discharge run PWM command value prepared coincident with the electric power command value. It should be noted that, during the stand-by run mode, this command value may be set to 0.
In addition, in a case where the instantaneous voltage drop or the service interruption occurs, the controller opens a passage of high-speed switch 6 shown in FIG. 2 and changes change switch 40 shown in FIG. 3 to self-contained run PWM command value preparing section 30, namely, self-contained run (AVR control). The self-contained run means that self-contained run discharges the electric power stored in electric power storage section 2 to make an effective value of PCS alternating current voltage coincident with the command value. This control permits a maintenance of the electric power supply to important load 5 even if the instantaneous voltage drop or the service interruption occurs.
As PCS 10 shown in FIG. 2, for example, described is in a non-patent document 1 is well known.
Non-patent document 1: PCS for NAS cell having functions of instantaneous voltage drop or service interruption counter-measure (MEIDEN REVIEW, pages 22 to 25 of 2006 No. 3).